As a type of high-energy density secondary cell, there has been proposed a non-aqueous solvent-type lithium secondary cell using a carbonaceous material for the negative electrode (e.g., Japanese Laid-Open Patent Appln. (JP-A) 57-208079, JP-A 62-90863, JP-A 62-122066 and JP-A 02-66856). The cell utilizes a phenomenon that a carbon intercalation compound of lithium can be easily formed electrochemically, and when the cell is charged, lithium in the positive electrode comprising, e.g., a chalcogenide compound, such as LiCoO2, is electrochemically inserted between carbon layers in the negative electrode (doping). The carbon thus doped with lithium functions as a lithium electrode to cause a discharge, whereby the lithium is liberated (de-doped) from the carbon layers to return to the positive electrode.
For a carbonaceous material as such a negative electrode material, or also for a carbonaceous material as a positive electrode material doped with lithium source, an amount of electricity utilizable per unit weight is determined by a lithium-dedoping capacity, so that such an electrode-forming carbonaceous material should desirably have a large lithium-dedoping capacity.
In recent years, along with development of various portable appliances, there has been an increasing demand for a secondary cell of a higher energy density as a power supply for such appliances. For this reason, it has been proposed to use as an active substance of negative electrode various intermetallic compounds having a larger capacity per volume than a carbonaceous material which is doped with lithium in the form of atoms, because such intermetallic compounds can be doped with lithium in the form of ions having a much smaller size than the atoms at least at a higher rate than a carbonaceous material (e.g., JP-A 11-86853).
However, a non-aqueous solvent secondary cell using such an intermetallic compound as a negative electrode material suffers from a problem of wasting lithium in the positive electrode because of a large irreversible capacity (non-dedoping capacity) expressed as a difference between the doping capacity and the dedoping capacity of lithium in the intermetallic compound, and also a problem of an inferior secondary cell cycle characteristic (repetitive charge-discharge performance) due to crystal structure destruction and fine powder formation of the inter-metallic compound caused by repetitive expansion and contraction accompanying the repetition of doping-dedoping cycles in the inter-metallic compound.